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  <title>Standard C Date &amp; Time</title>
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  <div class="header-box">
    <a href="../index.html">cppreference.com</a> &gt; <a href=
    "index.html">Standard C Date &amp; Time</a>
  </div>

  <div class="name-format">
    asctime
  </div>

  <div class="syntax-name-format">
    Syntax:
  </div>
  <pre class="syntax-box">
  #include &lt;time.h&gt;
  char *asctime( const struct tm *ptr );
</pre>

  <p>The function asctime() converts the time in the struct
  &#39;ptr&#39; to a character string of the following format:</p>
  <pre class="example-code">
   day month date hours:minutes:seconds year            
</pre>

  <p>An example:</p>
  <pre class="example-code">
   Mon Jun 26 12:03:53 2000             
</pre>

  <div class="related-name-format">
    Related topics:
  </div>

  <div class="related-content">
    <a href="clock.html">clock</a><br>
    <a href="ctime.html">ctime</a><br>
    <a href="difftime.html">difftime</a><br>
    <a href="gmtime.html">gmtime</a><br>
    <a href="localtime.html">localtime</a><br>
    <a href="mktime.html">mktime</a><br>
    <a href="time.html">time</a>
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<hr>

  <div class="name-format">
    clock
  </div>

  <div class="syntax-name-format">
    Syntax:
  </div>
  <pre class="syntax-box">
  #include &lt;time.h&gt;
  clock_t clock( void );
</pre>

  <p>The clock() function returns the processor time since the program
  started, or -1 if that information is unavailable. To convert the
  return value to seconds, divide it by CLOCKS_PER_SEC. (Note: if your
  compiler is POSIX compliant, then CLOCKS_PER_SEC is always defined as
  1000000.)</p>

  <div class="related-name-format">
    Related topics:
  </div>

  <div class="related-content">
    <a href="asctime.html">asctime</a><br>
    <a href="ctime.html">ctime</a><br>
    <a href="time.html">time</a>
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<hr>

  <div class="name-format">
    ctime
  </div>

  <div class="syntax-name-format">
    Syntax:
  </div>
  <pre class="syntax-box">
  #include &lt;time.h&gt;
  char *ctime( const time_t *time );
</pre>

  <p>The ctime() function converts the calendar time time to local time
  of the format:</p>
  <pre class="example-code">
   day month date hours:minutes:seconds year            
</pre>

  <p>using ctime() is equivalent to</p>
  <pre class="example-code">
   asctime( localtime( tp ) );          
</pre>

  <div class="related-name-format">
    Related topics:
  </div>

  <div class="related-content">
    <a href="asctime.html">asctime</a><br>
    <a href="clock.html">clock</a><br>
    <a href="gmtime.html">gmtime</a><br>
    <a href="localtime.html">localtime</a><br>
    <a href="mktime.html">mktime</a><br>
    <a href="time.html">time</a>
  </div>
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<hr>

  <div class="name-format">
    difftime
  </div>

  <div class="syntax-name-format">
    Syntax:
  </div>
  <pre class="syntax-box">
  #include &lt;time.h&gt;
  double difftime( time_t time2, time_t time1 );
</pre>

  <p>The function difftime() returns <em>time2</em> - <em>time1</em>,
  in seconds.</p>

  <div class="related-name-format">
    Related topics:
  </div>

  <div class="related-content">
    <a href="asctime.html">asctime</a><br>
    <a href="gmtime.html">gmtime</a><br>
    <a href="localtime.html">localtime</a><br>
    <a href="time.html">time</a>
  </div>
  </div>
  </td>
  


  </tr>
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<hr>

  <div class="name-format">
    gmtime
  </div>

  <div class="syntax-name-format">
    Syntax:
  </div>
  <pre class="syntax-box">
  #include &lt;time.h&gt;
  struct tm *gmtime( const time_t *time );
</pre>

  <p>The gmtime() function returns the given <em>time</em> in
  Coordinated Universal Time (usually Greenwich mean time), unless
  it&#39;s not supported by the system, in which case
  <strong>NULL</strong> is returned. Watch out for <a href=
  "../static_return.html">static return</a>.</p>

  <div class="related-name-format">
    Related topics:
  </div>

  <div class="related-content">
    <a href="asctime.html">asctime</a><br>
    <a href="ctime.html">ctime</a><br>
    <a href="difftime.html">difftime</a><br>
    <a href="localtime.html">localtime</a><br>
    <a href="mktime.html">mktime</a><br>
    <a href="strftime.html">strftime</a><br>
    <a href="time.html">time</a>
  </div>
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<hr>

  <div class="name-format">
    localtime
  </div>

  <div class="syntax-name-format">
    Syntax:
  </div>
  <pre class="syntax-box">
  #include &lt;time.h&gt;
  struct tm *localtime( const time_t *time );
</pre>

  <p>The function localtime() converts calendar time time into local
  time. Watch out for the <a href="../static_return.html">static
  return</a>.</p>

  <div class="related-name-format">
    Related topics:
  </div>

  <div class="related-content">
    <a href="asctime.html">asctime</a><br>
    <a href="ctime.html">ctime</a><br>
    <a href="difftime.html">difftime</a><br>
    <a href="gmtime.html">gmtime</a><br>
    <a href="strftime.html">strftime</a><br>
    <a href="time.html">time</a>
  </div>
  </div>
  </td>
  


  </tr>
  </table>
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<hr>

  <div class="name-format">
    mktime
  </div>

  <div class="syntax-name-format">
    Syntax:
  </div>
  <pre class="syntax-box">
  #include &lt;time.h&gt;
  time_t mktime( struct tm *time );
</pre>

  <p>The mktime() function converts the local time in <em>time</em> to
  calendar time, and returns it. If there is an error, -1 is
  returned.</p>

  <div class="related-name-format">
    Related topics:
  </div>

  <div class="related-content">
    <a href="asctime.html">asctime</a><br>
    <a href="ctime.html">ctime</a><br>
    <a href="gmtime.html">gmtime</a><br>
    <a href="time.html">time</a>
  </div>
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<hr>

  <div class="name-format">
    setlocale
  </div>

  <div class="syntax-name-format">
    Syntax:
  </div>
  <pre class="syntax-box">
  #include &lt;locale.h&gt;
  char *setlocale( int category, const char * locale );
</pre>

  <p>The setlocale() function is used to set and retrieve the current
  locale. If <em>locale</em> is <strong>NULL</strong>, the current
  locale is returned. Otherwise, <em>locale</em> is used to set the
  locale for the given <em>category</em>.</p>

  <p><em>category</em> can have the following values:</p>

  <table class="code-table">
    <tr>
      <th class="code-table-th">Value</th>

      <th class="code-table-th">Description</th>
    </tr>

    <tr>
      <td class="code-table-td">LC_ALL</td>

      <td class="code-table-td">All of the locale</td>
    </tr>

    <tr>
      <td class="code-table-td">LC_TIME</td>

      <td class="code-table-td">Date and time formatting</td>
    </tr>

    <tr>
      <td class="code-table-td">LC_NUMERIC</td>

      <td class="code-table-td">Number formatting</td>
    </tr>

    <tr>
      <td class="code-table-td">LC_COLLATE</td>

      <td class="code-table-td">String collation and regular expression
      matching</td>
    </tr>

    <tr>
      <td class="code-table-td">LC_C<a href=
      "../containers.html">TYPE</a></td>

      <td class="code-table-td">Regular expression matching,
      conversion, case-sensitive comparison, wide character functions,
      and character classification.</td>
    </tr>

    <tr>
      <td class="code-table-td">LC_MONETARY</td>

      <td class="code-table-td">For monetary formatting</td>
    </tr>

    <tr>
      <td class="code-table-td">LC_MESSAGES</td>

      <td class="code-table-td">For natural language messages</td>
    </tr>
  </table>

  <div class="related-name-format">
    Related topics:
  </div>

  <div class="related-content">
    (Standard C String and Character) <a href=
    "../stdstring/strcoll.html">strcoll</a>
  </div>
  </div>
  </td>
  


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<hr>

  <div class="name-format">
    strftime
  </div>

  <div class="syntax-name-format">
    Syntax:
  </div>
  <pre class="syntax-box">
  #include &lt;time.h&gt;
  size_t strftime( char *str, size_t maxsize, const char *fmt, struct tm *time );
</pre>

  <p>The function strftime() formats date and time information from
  <em>time</em> to a format specified by <em>fmt</em>, then stores the
  result in <em>str</em> (up to <em>maxsize</em> characters). Certain
  codes may be used in <em>fmt</em> to specify different types of
  time:</p>

  <table class="code-table">
    <tr>
      <th class="code-table-th">Code</th>

      <th class="code-table-th">Meaning</th>
    </tr>

    <tr>
      <td class="code-table-td">%a</td>

      <td class="code-table-td">abbreviated weekday name (e.g.
      Fri)</td>
    </tr>

    <tr>
      <td class="code-table-td">%A</td>

      <td class="code-table-td">full weekday name (e.g. Friday)</td>
    </tr>

    <tr>
      <td class="code-table-td">%b</td>

      <td class="code-table-td">abbreviated month name (e.g. Oct)</td>
    </tr>

    <tr>
      <td class="code-table-td">%B</td>

      <td class="code-table-td">full month name (e.g. October)</td>
    </tr>

    <tr>
      <td class="code-table-td">%c</td>

      <td class="code-table-td">the standard date and time string</td>
    </tr>

    <tr>
      <td class="code-table-td">%d</td>

      <td class="code-table-td">day of the month, as a number
      (1-31)</td>
    </tr>

    <tr>
      <td class="code-table-td">%H</td>

      <td class="code-table-td">hour, 24 hour format (0-23)</td>
    </tr>

    <tr>
      <td class="code-table-td">%I</td>

      <td class="code-table-td">hour, 12 hour format (1-12)</td>
    </tr>

    <tr>
      <td class="code-table-td">%j</td>

      <td class="code-table-td">day of the year, as a number
      (1-366)</td>
    </tr>

    <tr>
      <td class="code-table-td">%m</td>

      <td class="code-table-td">month as a number (1-12). Note: some
      versions of Microsoft Visual C++ may use values that range from
      0-11.</td>
    </tr>

    <tr>
      <td class="code-table-td">%M</td>

      <td class="code-table-td">minute as a number (0-59)</td>
    </tr>

    <tr>
      <td class="code-table-td">%p</td>

      <td class="code-table-td">locale&#39;s equivalent of AM or
      PM</td>
    </tr>

    <tr>
      <td class="code-table-td">%S</td>

      <td class="code-table-td">second as a number (0-59)</td>
    </tr>

    <tr>
      <td class="code-table-td">%U</td>

      <td class="code-table-td">week of the year, (0-53), where week 1
      has the first Sunday</td>
    </tr>

    <tr>
      <td class="code-table-td">%w</td>

      <td class="code-table-td">weekday as a decimal (0-6), where
      Sunday is 0</td>
    </tr>

    <tr>
      <td class="code-table-td">%W</td>

      <td class="code-table-td">week of the year, (0-53), where week 1
      has the first Monday</td>
    </tr>

    <tr>
      <td class="code-table-td">%x</td>

      <td class="code-table-td">standard date string</td>
    </tr>

    <tr>
      <td class="code-table-td">%X</td>

      <td class="code-table-td">standard time string</td>
    </tr>

    <tr>
      <td class="code-table-td">%y</td>

      <td class="code-table-td">year in decimal, without the century
      (0-99)</td>
    </tr>

    <tr>
      <td class="code-table-td">%Y</td>

      <td class="code-table-td">year in decimal, with the century</td>
    </tr>

    <tr>
      <td class="code-table-td">%Z</td>

      <td class="code-table-td">time zone name</td>
    </tr>

    <tr>
      <td class="code-table-td">%%</td>

      <td class="code-table-td">a percent sign</td>
    </tr>
  </table>

  <p>The strftime() function returns the number of characters put into
  <em>str</em>, or zero if an error occurs.</p>

  <div class="related-name-format">
    Related topics:
  </div>

  <div class="related-content">
    <a href="gmtime.html">gmtime</a><br>
    <a href="localtime.html">localtime</a><br>
    <a href="time.html">time</a>
  </div>
  </div>
  </td>
  


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  </table>
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<hr>

  <div class="name-format">
    time
  </div>

  <div class="syntax-name-format">
    Syntax:
  </div>
  <pre class="syntax-box">
  #include &lt;time.h&gt;
  time_t time( time_t *time );
</pre>

  <p>The function time() returns the current time, or -1 if there is an
  error. If the argument &#39;time&#39; is given, then the current time
  is stored in &#39;time&#39;.</p>

  <div class="related-name-format">
    Related topics:
  </div>

  <div class="related-content">
    <a href="asctime.html">asctime</a><br>
    <a href="clock.html">clock</a><br>
    <a href="ctime.html">ctime</a><br>
    <a href="difftime.html">difftime</a><br>
    <a href="gmtime.html">gmtime</a><br>
    <a href="localtime.html">localtime</a><br>
    <a href="mktime.html">mktime</a><br>
    (Other Standard C Functions) <a href=
    "../stdother/srand.html">srand</a><br>
    <a href="strftime.html">strftime</a>
  </div>
  </div>
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